A large number of people, such as those suffering from conditions such as diabetes, use some form of infusion therapy, such as daily insulin infusions, to maintain close control of their glucose levels. Currently, in the insulin infusion treatment example, there are two principal modes of daily insulin therapy. The first mode includes syringes and insulin pens. These devices are simple to use and are relatively low in cost, but they require a needle stick at each injection typically three to four times per day. The second mode includes infusion pump therapy, which entails the purchase of an expensive pump that lasts for about three years. The high cost (roughly 8 to 10 times the daily cost of syringe therapy) and limited lifetime of the pump are high barriers to this type of therapy. Insulin pumps also represent relatively old technology and are cumbersome to use. From a lifestyle standpoint, moreover, the tubing (known as the “infusion set”) that links the pump with the delivery site on the patient's abdomen is very inconvenient and the pumps are relatively heavy, making carrying the pump a burden. From a patient perspective, however, the overwhelming majority of patients who have used pumps prefer to remain with pumps for the rest of their lives. This is because infusion pumps, although more complex than syringes and pens, offer the advantages of continuous infusion of insulin, precision dosing and programmable delivery schedules. This results in closer glucose control and an improved feeling of wellness.
Interest in better therapy is on the rise, accounting for the observed growth in pump therapy and increased number of daily injections. In this and similar infusion examples, what is needed to fully meet this increased interest is a form of insulin delivery or infusion that combines the best features of daily injection therapy (low cost and ease of use) with those of the insulin pump (continuous infusion and precision dosing) and that also avoids the disadvantages of each.
Several attempts have been made to provide ambulatory or “wearable” drug infusion devices that are low in cost and convenient to use. Some of these devices are intended to be partially or entirely disposable. In theory, devices of this type can provide many of the advantages of an infusion pump without the attendant cost and inconvenience. Unfortunately, however, many of these devices suffer from disadvantages including patient discomfort (due to the gauge and/or length of injection needle used), compatibility and interaction between the substance being delivered and the materials used in the construction of the infusion device, and possible malfunctioning if not properly activated by the patient (for example, “wet” injections resulting from premature activation of the device). Difficulties in manufacturing and in controlling needle penetration depth have also been encountered, particularly when short and/or fine-gauge injection needles are used. The possibility of needle-stick injuries to those who come into contact with the used device has also been problematic.
Accordingly, a need exists for an alternative to current infusion devices, such as infusion pumps for insulin, that further provides simplicity in manufacture and use improvements for insulin and non-insulin applications.